Now, I am studying in Toyama University, Japan. I will do a research about degradation of water pollutant by TiO2 photocatalytic. The point is I want to know about detail preparation of transparent TiO2 thin film. Please tell me if know about that.

Replies: Posted By: M.Prassas
Date Posted: 06 November 2001 at 2:32am

There is a myriad of TiO2 preparation recipes. Follows one I have worked on

170 cc Iso propanol 12 cc Ti(isoPro)4 0.4 cc HCl 2M (10 min.)

Mix Ti precursor and Alcohol. Add drop by drop under stirring the HCl Wait 24h before making a coating. The solution can be deposited either by spinning or dipping. Cure the film at 120°C 1h and if needed at higher temperature.

Varying the HCl content can drastically changes the textural properties of the film. Try it.

Good luck

-------------

Posted By: fmvichi
Date Posted: 09 December 2002 at 1:36pm

There are other recipes:

I have successfully prepared transparent TiO2 films the following way:

200 mL deionized water

13 mL Ti isopropoxide

3 mL Conc. nitric acid

Mix water and acid. Add alcoxide slowly. A suspension is formed, which after 5-8 days becomes translucent - a sol. Use this to coat yor substrate by dip-coating, slip-casting or spin-coating.

Good Luck

Posted By: gabonino
Date Posted: 27 December 2002 at 10:00pm

fmvichi:

Do you have by any chance some information about a preparation using two Precursors: TEOS and Ti(iPr)4 ? I would sincerely appreciate some information about it

Regarding the receipe provided by M Prassas (given in the first reply to this topic), i have found that it gives quite good thin coatings. However, the sol gels very fast (two days). Is there a way to prepare sol lasting for say 10 days?

Regards

Posted By: administrator
Date Posted: 02 January 2003 at 9:52am

You have three ways to increase the pot life of your solution:

1. Decrease the HCl/Ti(OR)4 ratio

2. Decrease Ti(OR)4 /Iso propanol ratio

3. Do both

Good Luck

-------------Administrator
More you give more you get

Posted By: Muepfi
Date Posted: 04 February 2003 at 5:04am

Dear Fmvichi,

I tried to prepare thin TiO2 thin films by using your recipe. The preparation of the sol worked well (it became translucent after only one day).

But the deposition by dip-coating (0,2 cm/s) on soda-lime glass doensn't worked. I've got problems with the wettability. Any ideas what's wrong????

thank you for any kind of help.

best wishes

Heike Stuhldreher

Posted By: administrator
Date Posted: 06 February 2003 at 9:53am

Try M.Prassas recipe. ADVANCEST said that it works great.

-------------Administrator
More you give more you get

Posted By: xyuan
Date Posted: 14 February 2003 at 6:19pm

There are streaks emanating from the center of the wafer for SPIN-coated TiO2 films. Does anyone know how to solve the problem? The sol is transparent and can last at least a week or even longer. Thanks very much.

Posted By: Nai74
Date Posted: 19 February 2003 at 11:35am

Urgent!

hi, I had deposited thin film of TiO2 on sapphire. But, It 's important for me to remove in order to use the sapphire crystal. What's the mean manner or technique used?

There are streaks emanating from the center of the wafer for SPIN-coated TiO2 films. Does anyone know how to solve the problem? The sol is transparent and can last at least a week or even longer. Thanks very much.

****

This is because of uneven temperature distribution. The rotor of the spin coater is hot. The centr of the coated sol is dried faster.

-------------ASTC

Posted By: Barrie
Date Posted: 26 February 2003 at 8:17am

Hello,

I am attempting to dip coat TiO2 onto a polycarbonate (Lexan®) substrate (withdrawal speed variable). The problem is that the thin film cracks during the curing process (100C/1hour). These cracks do not present themselves when using a glass substrate. Any advice on how to eliminate or reduce these cracks would be much appreciated.

Thanks,

Barrie

Researcher, UMCS

Posted By: ChiangAST
Date Posted: 26 February 2003 at 9:23pm

Coating on hydrophobic polymer such as PC with alcohol/aqueous sol is more difficult then on glass. Some have suggested the use of plasma to creat hydroxyl on the surface to increase bonding.

The problem is strongly related to the titania sol used. There are commercial product that is made of PC coated with TiO2, or TiO2-SiO2 AR layer.

Silane coupling agent would also be helpful. Dilution of the sol so that the coated layer is thinner always reduce chance for cracking.

-------------ASTC

Posted By: waterace
Date Posted: 07 May 2003 at 10:15am

New to the world of sol-gel but trying to coat glass slides, have tried a few different methods for preparing sol-gel but not had too much success! what do you all find to be the most reproducible?

Has anyone tried to coat sand? If so did you have any luck?

Posted By: gabonino
Date Posted: 16 July 2003 at 10:41am

I have a question about the proccess for titania:

After hydrolysis and condensation, a big precipitate appears due to the formation of TiO2. Is it possibleto remove this precipitate and peptize it in some other media? If it is, what is the mechanism of this peptization process?

I tried using aqueous ammonia as a catalyst and peptizing agent for hydrolysis and condensation. A white suspension is formed, but I am not sure if it will become traslucent after some time....so I ask: Is it possible to use ammonia fdor coatings? How much would the properties of the coating differ from those prepared with acid catalysts?

Try peptizing with strong acids. This will probaly leads to transparent to translucent (depending of the ratio acid/TiO2) solutions ready for coating.

-------------Administrator
More you give more you get

Posted By: ChiangAST
Date Posted: 09 September 2003 at 12:08am

Quote: Originally posted by Administrator on 03 September 2003
Try peptizing with strong acids. This will probaly leads to transparent to translucent (depending of the ratio acid/TiO2) solutions ready for coating.

-------------ASTC

Posted By: ChiangAST
Date Posted: 09 September 2003 at 12:10am

Our experience is to peptize TiO2 at about pH=1.5. This will give a transparent sol. However, leaving the sol at this pH too long will cause the growth of TiO2 crystals.

-------------ASTC

Posted By: gabonino
Date Posted: 11 September 2003 at 7:47pm

ChiangAST,

how do you change this pH after achieving the formation of a stable colloidal dispersion? addition of a base? adition of some kind of counterion? further dillution?

Anyway, I got another question for the forum. Everybody has been commenting dip coating techniques. If I intend to use electrodeposition as the technique to obtain the coating, what should I do? Are there any useful references for titania you could let me know? which wuold be the conditions for this electrophoretic way?

I'm new to the sol gel chemistry...the posted recipe is very useful to my research study...I would like to know the way to incorporate zeolite into TiO2 film...are two percusors required?

Besides, can you tell the lifetime of the film after coating? any regeneration method to keep the film more long lasting?

Thanks in advance!!

Rgd,

Esther

Posted By: administrator
Date Posted: 08 October 2003 at 4:20am

Studies which make uses of recipes in this forum can be referenced by reporting this link

http://www.solgel.com">http://www.solgel.com at http://www.solgel.com/forum/display_topic_threads.asp?ForumID=4&TopicID=110&ReturnPage=&PagePosition=1&ThreadPage=1">http://www.solgel.com/forum/display_topic_threads.asp?ForumID=4&TopicID=110&ReturnPage=&PagePosition=1&ThreadPage=1

Thanks in advance

-------------Administrator
More you give more you get

Posted By: vedichi
Date Posted: 07 November 2003 at 9:01am

hai!

i am doing research in the field of thin film solar cells, urgently i need the reference Journal papers in the topic of " study of FT-Raman spectrsopy in Tio2 thin films". plz kindly guide me in light way,

thaks a lot for ur valuable refrences. it is very useful for my research work. once again i convey my hearty thanks to u.

vedichi

Posted By: pojengwang
Date Posted: 24 February 2004 at 12:43am

I have tried to synthesis titania sol. It contains 14.5wt% titania after peptizing it on pH=1.5. But after stirring for 9 days it solidify to jelly like a jam. Does anyone understand why it happens?

Thank you!

Posted By: ceec
Date Posted: 02 March 2004 at 1:55am

By the recipe of M.Prassas or other sol-gel method, could anyone describe how the gel looks like when it is said to be ready for experiment or coating? I don't know if mine has been over since I got pale white jam!!

Thx!!

Posted By: M.Prassas
Date Posted: 02 March 2004 at 3:24am

After prepapring the solution you should wait at least 24 hours before making a coating. The solution it looks water clear (depends of the purity of your initial precursor it may be also light yellow). If you want to preserve the solution from gelation you may need to keep it in a refrigerator. In this way you can have a workable solution for months.

I hope this can help

Posted By: ceec
Date Posted: 02 March 2004 at 9:41pm

thx for your prompt reply ^^...do you mean the color and texture of the solution shouldn't be changed (remains light yellow) after 24 hours?

Posted By: gabonino
Date Posted: 04 March 2004 at 1:14pm

ceec,

I tried Prasas' recipe, and it seems to be quite stable during the very first days: however, after a while, it begins to get too viscous, ending up in the formation of a pale white gel. My solution was almost clear, having the yellow color only after drying it. The time Dr. Prasas tells you about is going to help you with the formation of better chains of TiO2, suitable for your coating....this change, however, will remain unseen under the eyes

sorry for bothering again...the coating crystallined at only 100 heating...some crystals stay on the film but not coated...can you tell if I need to stirr the solution after the addition of HCl...'cos I found there some ppt formed when HCl is added even with very slow speed by a syringe...any ways to solve this?

Posted By: DEARWL
Date Posted: 11 May 2004 at 8:59am

Dear FORUM

This is my first to there,i have a problem how can i do the TEM of the TiO2 films on the galss?

thanks!

-------------THANK

Posted By: HoKra
Date Posted: 12 May 2004 at 7:33am

Hi Forum Members,

I tried to use a binary TiO-SiO sol. I know that a lot of work has been done around this system. However, I faced problems when I tried to mix a sol made of Ti(isoPro)4 with one containing TEOS. Lots of TiO2-precipitates fell out and the sol became a white suspension. Does anyone of you know a recipe for both starting sols which will lead to a transparent binary sol?

Holger Krause

Student of Microsystemtechnology

IMTEK Freiburg, Germany

Posted By: rammahipal
Date Posted: 28 May 2004 at 12:00pm

Hi

I tried to prepare TiO2 Soln by using Titanium ispropoxide(5ml),Ethanol(35ml) and acetic acid(0.5ml)

but the soln remained white even after 12hrs.

did one some one prepared the soln by this method.

the soln formed is white

Iam not sure whether the soln for med is right or not.

can some one suggest me in this regard

-------------Ram
Chemical Engineering)
University of arkansas
USA

Posted By: HoKra
Date Posted: 01 June 2004 at 10:12am

Hi Ram,

try to start with the recipe from M.Prassas (see first Page of the Forum). I used it with several modification concerning the amount of isopropanol.

I used the following way:

Volumratio Ti(isoPro):isoPro:HCl-2M = 12:60:0,4

Pour the Ti(isoPro) under stirring to the isoPro and ad afterwards the HCl.

The solution becomes transparent after less the 1 hour. However, there may appear some precipitates (not much). Therefor I used a syringe filter (0,2µm pores) to fill the sol in a container for storage. The sol will remain stable if cooled (3°C) for many days (it did not gel after 3 weeks, if cooled).

I also tried to use it with Ethanol instead of Isopropanol. Right after mixing, the sol was transparent, but after 15 min it became white because of precipitates of TiO altough I used a glovebox with a Nitrogen atmospere. Therefor I think that it is difficult to create a stable Sol using ethanol.

the ratio of isoproponal/TiO2 was decreased from the one which M.Prassas Mentioned.

as per what administrator said as u increase the ratio of proponal to TIO2 precursor the soln remains stable for long time.

any way thanks for your mail.

i will try with your recipe.

regards

-------------Ram
Chemical Engineering)
University of arkansas
USA

Posted By: HoKra
Date Posted: 03 June 2004 at 5:19am

Hi Ram,

the reason why I am using less Isopropanol is because I would like to decrease the shrinkage. It is correct that a higher ratio of isopropanol/ Ti(isopro) increases the stability of the sol, but on the other hand it also increases the volume-loss of the xerogel. It depends on the thickness you would like to reach and the coating technique you apply which ratio fits best for your application.

i tried ur recipe but as soon as i added Ti precursor and HCL the solution become gel with in 5 min.i tried twice.

any further u would like to give.

but thanks for your response.

danken sie.

-------------Ram
Chemical Engineering)
University of arkansas
USA

Posted By: HoKra
Date Posted: 04 June 2004 at 5:44am

Hi Ram,

Do you heat the sol while stirring? I am preparing the sol at room temperature without any heating. I mix the ingredients in a nitrogen flooded glove box (humidity is <20%) under stirring (400-500rpm, depending on the total volume). One thing may also be important. The isopropanol is volatile, therefor I cover the beaker with a watch glass to reduce solvent loss during preparation. Maybe you should try to vary the catalyst solution. I used a 2M HCl solution, prepared by adding concentrated HCl to DI-Water. The amount I mentioned in the recipe is the amount of the 2M solution (not concentrated HCl). Actually I can“t think of any other reason then heating and amount of catalyst which would lead to such a fast gelling.

it is right that you receive thinner coatings with increased isopropanol/Ti(isoPro) -ratio. As I wrote, the volume loss, therefor the shrinkage, is also increased. The shrinkage will take place mostly in perpendicular direction to the substrate if you apply thin coatings (<1µm). That is due to the adhesion forces of the gel to the substrate, it will prevent the shrinkage in lateral dimensions.

i did the experiment in a hood not in a nitrogen atmosphere that might be the reason for not working.

once again thanks lot for ur reply

i will try to work it in nitrogen environemnt glove box

regards

-------------Ram
Chemical Engineering)
University of arkansas
USA

Posted By: loubna
Date Posted: 04 June 2004 at 2:26pm

Quote: Originally posted by Dhanus on 06 November 2001

Now, I am studying in Toyama University, Japan. I will do a research about degradation of water pollutant by TiO2 photocatalytic. The point is I want to know about detail preparation of transparent TiO2 thin film. Please tell me if know about that.

hy, i am studying in Faculty of science in Morrocco. i will do the same research but is only the second part of my research. my TiO2 thin films is prepared by the sol gel method

-------------Bamoulid

Posted By: rammahipal
Date Posted: 04 June 2004 at 3:20pm

Hi

i user M.Prassas recipe for making TiO2 film ,the soln i prepred.i kept some quantity of it in refrigerator and other beaker of soln in room temp.

the one which i kept in room temp become fully gel soln by the time after 12hrs

i user M.Prassas recipe for making TiO2 film ,the soln i prepred.i kept some quantity of it in refrigerator and other beaker of soln in room temp. the one which i kept in room temp become fully gel soln by the time after 12hrs

i used 0.2 ml 2M Hcl

the one which i kept in refrigerator in still liq soln.

did it happen for anyone, or else is there any mistake i did.

---------------------------------------------------------------------

Hi rammahipal

Nothing wrong with that. At room temperature the sol is still reacting and therefore some how you will end up with a gel (depending on the initial concentrations and acidity, this can happens in hours, days or months). By putting your solution in a refrigerator you slow down the reactivity and therefore you increase its lifetime.

regards

-------------Administrator
More you give more you get

Posted By: gabonino
Date Posted: 06 June 2004 at 10:33pm

Hi,

regarding Mr Prasa's recipe, I have a question......I did the experiment with the quantities given, but the sol was quite stable and gelled in a period after a week, staying very stable; I live on a very high city, over 7500 feet high. Does this affect the behavior of the sol, or its gellation time?

I just wanted to make sure that the film formed is TIO2 film . i tried with spectorphotometer. But it didn't gave any useful information for me.

can any one of u suggest me regarding the characterization to know exactly about the film i made.

-------------Ram
Chemical Engineering)
University of arkansas
USA

Posted By: gabonino
Date Posted: 09 June 2004 at 8:55pm

Rammahipal,

you can try an EDX analysis......I do not know so well about the technique, but from what I have seen, you can make it at the same time you do a SEM. I hope this helps, and I hope someone elese gives further information about this, if I am right

i did the experiment in a hood not in a nitrogen atmosphere that might be the reason for not working.

once again thanks lot for ur reply

i will try to work it in nitrogen environemnt glove box

regards

Hi Holger,

Is that critical the preparation of sol should be in nitrogen atmosphere? We are lacking of such facility. Also, if I increase the TIP concentration, I can observe some big crystal on the substrate after drying at 100C. Any suggestion on it? Thx!

Posted By: rammahipal
Date Posted: 10 June 2004 at 12:57am

Hi

I used spectra photometer for abcsorbing UV Visible spectroscopy of the TiO2 Film formed.

Did some one worked on it.

as i wasn't able to get any greeat absorbance in the wave format and also the absorbance was too low.

is it due very thin film properties or any other reason

can some help me in this regard.

-------------Ram
Chemical Engineering)
University of arkansas
USA

Posted By: HoKra
Date Posted: 14 June 2004 at 3:42am

Hi Ceec,

the Ti(isopro) reacts pretty easy with the atmospheric water. I am not sure about the exact reaction, but you can see fog evaporating while preparing the sol. Also you have precipitates of TiO2 which will affect the sol stability.

First: Probably the purpose of the aging of the sol is to achieve more viscous sols, that will lead into thicker layers of the coating. I am not sure on such affirmation, but probably someone more involved with the process can contradict this theory.

Second: Thermal treatment is made on coatings in order to achieve several purposes; on those, I can mention densification, which will lead to a more densified coating, less porous and probably more resistant in mechanical matters. On the other side, thermal treatment can be used in order to achieve some specific structure for the coating. For instance, if you want rutile coatings, you should do a thermal treatment, so that you can get a complete transformation into this phase. Later on I hope to send you some other aspects that you can get once you make thermal treatment on a coating

i have one problem,the solution i prepared was stable during the very firt days,hovere after 2 days it begins to chang turbidity,ending up in the formation of a pale whit precipitates,please tell me the reason!

and i want to konw what is the mechanism of the peptization process?

-------------thank you

Posted By: gabonino
Date Posted: 30 August 2004 at 10:44am

wuji,

please contact me through e-mail, I got some articles regarding the peptization process. The change of the characteristics of the sol you preapre as time goes by might occur due to the aging process of the colloid, a very normal process in the lifetime of a sol. As titania tends to be a bit unstable, precipitates might form (I have seen this myself, sometimes they precipitate quickly, sometimes it takes a bit longer). A good thing to improve your sol shelf life could be a change in the pH of it. In this same forum, I think, someone actually recommended a change in the pH for a particular problem I had; I haven't been able to try, but you might want to contact this person, to ask how to change it.

What would be the following treatment of Mr. Prassas recipe to gain crystalline (anatase, rutile) TiO2-films? I am especially looking for treatments below 100°C. Thanks for your help.

Posted By: rammahipal
Date Posted: 06 September 2004 at 4:00pm

hi

i just wanted to know as u mentioned that by thermal treatment of film the film becomes less porous, what u suggest me as i want to make highly porous film of Tio2 and thin film

do u want me to make the film with out thermal treatment.

Quote: Originally posted by gabonino on 19 July 2004

Holger,

regarding your questions:

First: Probably the purpose of the aging of the sol is to achieve more viscous sols, that will lead into thicker layers of the coating. I am not sure on such affirmation, but probably someone more involved with the process can contradict this theory.

Second: Thermal treatment is made on coatings in order to achieve several purposes; on those, I can mention densification, which will lead to a more densified coating, less porous and probably more resistant in mechanical matters. On the other side, thermal treatment can be used in order to achieve some specific structure for the coating. For instance, if you want rutile coatings, you should do a thermal treatment, so that you can get a complete transformation into this phase. Later on I hope to send you some other aspects that you can get once you make thermal treatment on a coating

Best regards

-------------Ram
Chemical Engineering)
University of arkansas
USA

Posted By: gabonino
Date Posted: 06 September 2004 at 5:04pm

Ram Mahipal Kouda,

the better and more delicate the drying conditions, the mor porous material you will get...you can go from supercritical drying up to strong thermal treatment.....my suggestion is to try to remove solvents, each time getting one with higher vapor pressure...that might work, though structure will not remain monolitic.

i would like to know what do u mean by delicate conditions, and what is supercritical drying conditions

Quote: Originally posted by gabonino on 06 September 2004

Ram Mahipal Kouda,

the better and more delicate the drying conditions, the mor porous material you will get...you can go from supercritical drying up to strong thermal treatment.....my suggestion is to try to remove solvents, each time getting one with higher vapor pressure...that might work, though structure will not remain monolitic.

-------------Ram
Chemical Engineering)
University of arkansas
USA

Posted By: gabonino
Date Posted: 06 September 2004 at 5:51pm

ram mahipal,

I see you're online right now, have you got msn or yahoo messenger? if so, write me to my email and send it to me

hi, I had deposited thin film of TiO2 on sapphire. But, It 's important for me to remove in order to use the sapphire crystal. What's the mean manner or technique used?

thank you for help..

I have similar problem. I have deposited TiO2 on silicon wafer by spin-coating. However, i don't know how to etch it to expose the botton electrode.

Anyone have suggestions on that? wet etching is preferable.

Thanks!!!

Posted By: Guests
Date Posted: 09 September 2004 at 2:14am

Dear forum,

I am studying about TiO2 fabrication using sol gel method. Many researchers concern to explore alkoxide (Titanium Tetra iso Propoxide -TTIP) since the alkoxide offer the high pure material for Sol gel method. However, I found that it is not easy to control the Ti sol since the alkoxide is very reactive.The basic sol gel method that I know is based on the hydrolysis method. As I know, hydrolysis means reacting with water. Direct reaction of TTIP and water will result white precipitation soon after adding water into TTIP. This is the reason why people use alcohol as a steric hindrance to avoid the direct contact between TTIP and water. However, I could not understand, why researcher use acid (usually HCl) and even base (ammonia) during the hydrolysis reaction?

Could any body help me?

Thx!

Posted By: gabonino
Date Posted: 09 September 2004 at 12:27pm

Elly,

the reason for the usage of some electrolytes is not the hydrolysis reaction, biut the peptization process of the TiO2 generated; electrolytes help particles achieve de double layer neccesary for the stabilization of the colloid.

Thx for your reply. The first assumption I've ever tried to understand the adding of some electrolite is based on the knowledgment that some chemical reaction might be occur with specific condition (pH, temperature, etc). Then, I assume that the TTIP hydrolysis reaction will occur only in the relatively low temperature (T room) and specific pH. I realized that this 'specific pH' is unreliable reason because it could be acid or base. :( And, I think that your explanation about "electrolite help particle to stabilize the colloid" is reliable reason because it could explain the using of both acid and base electrolite during the reaction.

However, would you please tell me where I could find any literature about the double layer? I dont know what you mean by the 'double layer'.

thx.

Posted By: eexie
Date Posted: 09 September 2004 at 10:52pm

Hi, all experts

I am a freshman. I shall be very grateful if you could explain my experimental phenomena!

By adding PEG (polymer) into TiO2 (3 nm; 2 mol/L) water suspension solution, a transparent sol-gel could be fomed. After high T therm-treatment, a transparent film was obtained.

However, if TiO2 size was about 25 nm I only got pale ink-like solution. After high T therm-treatment, a pale film was formed.

How to get transparent sol-gel by using a suspensive solution of TiO2 (25nm) 40 wt% in water?

And then how to get transparent TiO2 film?

Thanks for help

-------------Xie

Posted By: adam1979
Date Posted: 10 September 2004 at 2:37am

J materials Science28(1993)2353-2360

the paper is one of the most great works in titania sol-gel processing.

Posted By: gabonino
Date Posted: 12 September 2004 at 4:12pm

Adam,

is there a chance you can get me (or us) the paper you reference on the forum? Do you have access to it?

I just did my first coatings of TiO2. But I still have questions about the procedure. When I add Tialkoxide to excess water (pH=1) a white precipitate instantly forms but dissolves after a while of stirring. Is the precipitate TiO(OH)? Then I heat my transparent solution up to about 80°C. After about 1hr I get a white suspension with very small particles.Do I do anthing wrong? Does it have to be transparent after heating?

Another question: How thick is your layer after one coating with spin-coating?

thanks very much for your help?

Sonja

Posted By: wuji
Date Posted: 21 September 2004 at 8:18am

dear Barrie:

i am sorry that i cann't help you to solve your problem. from your question i know that you can produce the crack free TiO2 films coated on glass. in my study i can get the crack free film but it is very thin which is only one layer.when we increase the layers the surface of the film can appear cracks,do you kown how to aviod this phenomena,pleaes help me! thanks a lot!

-------------thank you

Posted By: wuji
Date Posted: 21 September 2004 at 10:14pm

dear gabonino:

i wrote to you according your email,but i can't reach to you.i always received the back letter by the sysytem,so please tell me another email which can contact with you !

I get the above information from some journals. Can the sol gel be prepared in this way?

After heat treatment at 440 degree C and 850 degree C, a yellowish brownish coating is seen.Is that correct?

I have tried out the self cleaning effect after the heat treatment but cannot get any visible result.

Please help me with my questions.

Posted By: vedichi
Date Posted: 16 December 2004 at 7:44am

Dear Green bean

according your statment , the process is ok , but u should keep the Molarity ratio for the precursor and the solvents strictly, and the heat treatment is one of the predominant factor to change structure. so above 800 C u got the Rutile phase , but its photocatalitic and photoconductive nature lesser than the Anatase structure (400C800C). so u tried ur Self cleaning process with in the anatase strucutre .

the rutile structure is used for sensors , most generally no one use to photoconductive process...if u need help send the mail to my id mailto:vedichi@rediffmail.com">vedichi@rediffmail.com.

further literaure need search in the Solgelgatway.

all the best

vedichi

Posted By: sanjay
Date Posted: 21 December 2004 at 3:15am

Quote: Posted By Sanjay Gadakh

Now, I am doing research in K.T.H.M. College, Nasik, India. I am interested in preparing TiO2 thin films for use in dye sensitized solar cells. The point is I want to know about detail preparation of transparent TiO2 thin film. Please tell me about that.

-------------Sanjay Gadakh

Posted By: sandeep7
Date Posted: 12 January 2005 at 6:24pm

Hi All,

I have been trying to deposit TiO2 thin films and initially used Titanium isopropoxide, ethanol and acetic acid and my solution precipitated heavily probably because of not using absolute ethanol. I have tried to work M.Prassas's recipe and it was clear solution when alkoxide was mixed with isopropanol but on addition of HCL selective particulate precipitation occured. I would like to know, the reason for it and whats the exact role of HCL in the reaction. Does this mean that the sol-solution is unstable ? What role does the 24 hour waiting period before deposition leads to ?

Would be glad if you guys have answers for my basic questions.

Thanks

Posted By: greenbean1980
Date Posted: 12 January 2005 at 8:52pm

Regarding the 24 hr waiting period, the longer the waiting period the thicker will be the TiO2 coating.

Posted By: gabonino
Date Posted: 13 January 2005 at 5:37pm

sandeep,

due to the nature of transition metals, their alkoxides are highly unstable and react steadily with water, causing the formation of TiO2 particles way too quickly (precipitates). Because of this, a peptizing agent (the acid) is necessary, in order to establish the double layer necessary for the stability of the sol. In Prasas' recipe, the hydrogen chloride makes this, but, in theory, acetic acid may also work as peptizing agent. For further information, you may refer to Brinker's book, and an introduction to colloid chemistry, they might give you better hints and explain the process in detail.

I don't know what is what number 3 is called (retarder or something), but I can tell you what it does. It slows your hydrolisation reaction. The groups substitute your butanol-groups on your precursor and water has more trouble to react. That's the idea behind chemical 3:-)

Posted By: greenbean1980
Date Posted: 21 January 2005 at 12:17pm

What is the purpose of water? If water has more trouble to react, what will happen?

Posted By: sandeep7
Date Posted: 21 January 2005 at 1:11pm

Hi Oscar,

Thanks for your reply. I have been able to spin cast anatase TiO2 film though, I was trying to deposit rutile phase. I think by increase temperature, I would be able to accomplish it.

But still having problems with capacitance measurment, as it seems there are lot of bubbles entraped when I am spin coating the film.

Any pointers ?

Thanks a bunch for your help

Posted By: latingirl
Date Posted: 24 January 2005 at 1:32am

hai...

I'm a bachelor student and i'm doing a thesis about titanium dioxide photocatalytic. The problem here i still can't get a simply method to prepare the sol-gel and the thin film. The chemical that I will use is titanium (IV) isopropoxide. I hope you can help me because I need to find a method that would not use advance instruments

Posted By: greenbean1980
Date Posted: 24 January 2005 at 3:21am

Hi, latingirl. You can use the following chemical

1)Diethanolamine

2)titanium(IV) butoxide

3)ethanol

4)water

There are actually a lot of different ways to mix sol-gel. can be found in journals

Posted By: ceec
Date Posted: 24 January 2005 at 3:34am

hi all,

I've tried many times to prepare TiO2 by TIP, iso-propanol and HNO3. A clear sol formed after 1 day. Then it is coated on glass and followed by sucessive heating. But the performance of photoreaction of organic compound is poor (almost the same with or without the film)...can anyone help me to increase the efficiency?

Posted By: latingirl
Date Posted: 04 February 2005 at 10:47pm

Hai Greenbean,

Thanks for your reply. I'm on the step for preparing the sol gel- TiO2 but i'm concious about the uses of polyethylene glycol (PEG) in the sol gel preparation. Is it necessary? What is actually the function of PEG in sol gel- TiO2 preparation? What happen if i'm not use it in my preparation? Can it effet in the efficiency of my thin film coating?

Posted By: gabonino
Date Posted: 05 February 2005 at 7:18pm

Latingirl,

that is just one way recommended by greenbean; as he quoted, there are several different ways of preparing titania sols. Have you tried Prasas' recipe given on this same forum? I did, and the results are interesting. Perhaps diethanolamine is an agent that somehow retards condensation process of the alkoxide, I am not sure. If so, you may also try Acetyl Acetone; regarding this particular chemical you will find hundreds of articles

It's about the PEG and Titania interactions and what you can make from it with the right preparation. Also very many retarders are given...

Have fun reading, I enjoyed it...!!!

Posted By: latingirl
Date Posted: 17 February 2005 at 11:48pm

Can someone give me Prasa's recipe about the preparation of titania sols. because I like to try it.

Thanks.. I really appreciate it

Posted By: gabonino
Date Posted: 20 February 2005 at 8:09pm

Latingirl,

you can find this recipe on the page number one of this recipe; basically, it involves the addition of a small amount of concentrated acid (that already has water in it) into a solution of TIPT with Isopropanol....you can see the formation of a sol, than with time turns into a gel. If you are not familiarized with the process, I think it might be very useful, it helped me understand the process in a very good way

I already get the Prasas' Recipe but I'm confuse about certain part of the formula. Can any body explain to me more clearly? Unit that have been use is cc (for example 40.4cc TIP), the term of cc stand for what? Should or shouldn't I add binder (such as PEG) in the Prasas Recipe'? How I want to know the limit time (how long the sol gel can be used) of my sol gel when it completely been prepared?

Posted By: HAMAMA
Date Posted: 26 May 2005 at 7:50am

Quote: Originally posted by Nai74 on 19 February 2003

Urgent!

hi, I had deposited thin film of TiO2 on sapphire. But, It 's important for me to remove in order to use the sapphire crystal. What's the mean manner or technique used?

thank you for help..

-------------HAMAMA MOh

Posted By: sagebob
Date Posted: 27 May 2005 at 8:05pm

Howdy,

My experience with tetraethyltitanate (TET) and tetraisopropyltitanate (TIPT) was that they were too reactive with atmospheric water vapor. Using TBT and chelating materials works very well.

you might try:

add while stirring

34g ethyl acetoacetate

9g 2,4-pentanedione

160g TBT

978g ethyl alcohol (100%) denatured is OK

mix for 1 hour

coats glass well, fire at 350 to 550 C, hotter gives denser coating

if there are wetting problems, glass is dirty.

enjoy - bob

Posted By: sagebob
Date Posted: 27 May 2005 at 8:36pm

Howdy waterace,

Coating sand sounds interesting. I have coated glass beads. A little simpler probably. they were all about the same size and flowed easily.

Mix the sand with a DILUTE solgel solution. Spray the suspension into a heated airstream. If hot enough, for long ennough, sand is coated and does not stick together. Just igniting the sprayed solvent mixture does not heat them long enough and is not uniform. A nice display however.

--bob

Posted By: latingirl
Date Posted: 27 May 2005 at 11:21pm

Once again I ask the forum the same thing:

The term of cc in Prasas' Recipe stand for what? because before this I never

heard about this term. Should or shouldn't I added binder (such as PEG) in the